fix: drag-and-drop from a folder on the dock (closes #706)

alt-tab-macos.xcodeproj/project.pbxproj

@@ -22,6 +22,7 @@
 		BF0C823630E3DEAC576FAFE6 /* menubar-1@2x.png in Resources */ = {isa = PBXBuildFile; fileRef = BF0C88BF67CF4D71002A60EB /* menubar-1@2x.png */; };
 		BF0C828D53D429C2B8B22391 /* Localizable.strings in Resources */ = {isa = PBXBuildFile; fileRef = BF0C883EBA8FDA9CB61C91FD /* Localizable.strings */; };
 		BF0C829583ED47E458528F3A /* accessibility@2x.png in Resources */ = {isa = PBXBuildFile; fileRef = BF0C889529FF19620EDAC295 /* accessibility@2x.png */; };
+		BF0C832C5BF4C8E9C95F7767 /* MissionControl.swift in Sources */ = {isa = PBXBuildFile; fileRef = BF0C82E4DE5A28800F1DA6E6 /* MissionControl.swift */; };
 		BF0C8382435C0087E131BD83 /* InfoPlist.strings in Resources */ = {isa = PBXBuildFile; fileRef = BF0C8A900DA32A7F62457CC2 /* InfoPlist.strings */; };
 		BF0C83AB0186CC48FADF66A7 /* Localizable.strings in Resources */ = {isa = PBXBuildFile; fileRef = BF0C847B2D68EACFAC1B06D1 /* Localizable.strings */; };
 		BF0C83E902F75A97E8FD374A /* menubar-2@2x.png in Resources */ = {isa = PBXBuildFile; fileRef = BF0C8D3333653ACAEF730DD8 /* menubar-2@2x.png */; };
@@ -184,6 +185,7 @@
 		BF0C828AF7BCC4F47E70B28F /* menubar-2.svg */ = {isa = PBXFileReference; lastKnownFileType = file.svg; path = "menubar-2.svg"; sourceTree = "<group>"; };
 		BF0C82C381FCBCF8109735AC /* pl */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = text.plist.strings; name = pl; path = InfoPlist.strings; sourceTree = "<group>"; };
 		BF0C82D44C2DFAA5D8F60394 /* sq */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = text.plist.strings; name = sq; path = Localizable.strings; sourceTree = "<group>"; };
+		BF0C82E4DE5A28800F1DA6E6 /* MissionControl.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = MissionControl.swift; sourceTree = "<group>"; };
 		BF0C831AA76CF82EAC7B60B3 /* gl */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = text.plist.strings; name = gl; path = Localizable.strings; sourceTree = "<group>"; };
 		BF0C83258B2873D9CDC74EA5 /* preferences-controls.jpg */ = {isa = PBXFileReference; lastKnownFileType = image.jpeg; path = "preferences-controls.jpg"; sourceTree = "<group>"; };
 		BF0C833D471343CEA3DEFE56 /* icon_512x512@2x.png */ = {isa = PBXFileReference; lastKnownFileType = image.png; path = "icon_512x512@2x.png"; sourceTree = "<group>"; };
@@ -946,6 +948,7 @@
 				D04BA03200F5A8FC0CD03607 /* CGWindowID.swift */,
 				D04BA8DB8AA7E5570DAC568A /* Sysctl.swift */,
 				D04BA514F1C4B475B3CA6EB6 /* Bash.swift */,
+				BF0C82E4DE5A28800F1DA6E6 /* MissionControl.swift */,
 			);
 			path = "api-wrappers";
 			sourceTree = "<group>";
@@ -1665,6 +1668,7 @@
 				BF0C8C7E96DB48120462DA00 /* TrafficLightButton.swift in Sources */,
 				BF0C898511686611E4D7D81E /* Button.swift in Sources */,
 				BF0C8E16F38203AEC71E062B /* TableView.swift in Sources */,
+				BF0C832C5BF4C8E9C95F7767 /* MissionControl.swift in Sources */,
 			);
 			runOnlyForDeploymentPostprocessing = 0;
 		};

src/api-wrappers/CGWindow.swift

@@ -9,15 +9,6 @@ extension CGWindow {
         return CGWindowListCopyWindowInfo([.excludeDesktopElements, option], kCGNullWindowID) as! [CGWindow]
     }
 
-    static func isMissionControlActive() -> Bool {
-        // when Mission Control is active, the Dock process spawns some windows. We observe this side-effect and infer
-        for window in windows(.optionOnScreenOnly) {
-            guard window.ownerName() == "Dock", window.title() == nil else { continue }
-            return true
-        }
-        return false
-    }
-
     // workaround: filtering this criteria seems to remove non-windows UI elements
     func isNotMenubarOrOthers() -> Bool {
         return layer() == 0

src/api-wrappers/MissionControl.swift

@@ -0,0 +1,24 @@
+import Foundation
+
+class MissionControl {
+    static func isActive() -> Bool {
+        // when Mission Control is active, the Dock process spawns some windows. We observe this side-effect and infer
+        var missionControlHint = false
+        for window in CGWindow.windows(.optionOnScreenOnly) {
+            // ownerName == "Dock" && title == nil is a sign that Mission Control may be active
+            if window.ownerName() == "Dock" && window.title() == nil
+                   // layer == 500 can be a false positive when a user drags a file from a Dock folder
+                   // see https://github.com/lwouis/alt-tab-macos/issues/706
+                   && window.layer() != 500 {
+                return true
+            }
+        }
+        return false
+    }
+}
+
+enum MissionControlState {
+    case inactive
+    case expose
+    case showDesktop
+}

src/ui/App.swift

@@ -202,10 +202,11 @@ class App: AppCenterApplication, NSApplicationDelegate {
 
     func focusSelectedWindow(_ selectedWindow: Window?) {
         hideUi()
-        guard let window = selectedWindow, !CGWindow.isMissionControlActive() else { return }
+        if let window = selectedWindow, !MissionControl.isActive() {
-        window.focus()
+            window.focus()
-        if Preferences.cursorFollowFocusEnabled {
+            if Preferences.cursorFollowFocusEnabled {
-            moveCursorToSelectedWindow(window)
+                moveCursorToSelectedWindow(window)
+            }
         }
     }
 
@@ -258,7 +259,7 @@ class App: AppCenterApplication, NSApplicationDelegate {
         if isFirstSummon || shortcutIndex != self.shortcutIndex {
             debugPrint("showUiOrCycleSelection: isFirstSummon")
             isFirstSummon = false
-            if Windows.list.count == 0 || CGWindow.isMissionControlActive() { hideUi(); return }
+            if Windows.list.count == 0 || MissionControl.isActive() { hideUi(); return }
             // TODO: can the CGS call inside detectTabbedWindows introduce latency when WindowServer is busy?
             Windows.detectTabbedWindows()
             // TODO: find a way to update space info when spaces are changed, instead of on every trigger